This invention relates generally to machines for filling products into pails, tubs, and cartons, and particularly to a mechanism for separating nested plastic pails from a stack or column and sequentially delivering those pails to a filling station.
Different methods of separating the lowermost pail from a column of nested pails are known. The most frequently used methods include gripping the bottom of the lowermost pail using a selectively actuated vacuum or other suction gripping means, such as shown in U.S. Pat. Nos. 4,082,203; 4,157,767; or 4,285,187 to Schjeldahl, or alternately by a mechanical separation means such as the worm-type dispensers for rimmed containers shown in U.S. Pat. Nos. 3,849,970; 3,903,676; and 3,932,978 to Kinney, or U.S. Pat. No. 3,293,823 to Anderson.
U.S. Pat. No. 4,054,212 to Mueller discloses a cup dispensing apparatus where gripping fingers retain a horizontally oriented column of cups by gripping the rims of the nested cups while the endmost cup is positively driven toward a conveyor by pusher arms pivoting about a shaft.
U.S. Pat. Nos. 1,416,219 to Litchfield, 2,365,916 to Tarry, and 3,662,919 to Shmerling each disclose methods of bottom dispensing stacked containers utilizing a pivoting cog, finger, or lever to controllably release the lowermost pail of a column, and to retain the upper pails in the vertical column disposed above the remainder of the feed mechanism.
U.S. Pat. No. 3,584,431 to Flavelle discloses a method of separating the lowermost of a column of nested cups supported on their rims by wedges, the method using a bellows to produce a jet of air to blow the lowermost cup downwardly from the column and onto a conveyor.
Also of interest are U.S. Pat. No. 3,841,293 to Laporte which discloses an iris mechanism for dispensing items such as clay pigeons utilizing a retractable latch which pivots horizontally, and U.S. Pat. No. 3,622,040 to Putnam which discloses a mechanism for counting and dispensing a plurality of cups in a nested stack, the mechanism including two pair of horizontally movable tongue elements which engage the rims of the cups within a vertical tube.
U.S. Pat. No. 3,407,965 to Kuhlman discloses a denesting apparatus for shallow plates and pans utilizing a pair of rotating rollers with one-way clutches to frictionally contact the beveled exterior wall of the plate or pan and strip the plate or pan downwardly from the column. U.S. Pat. No. 3,858,732 to Kemper discloses a magazine for trays including a support surface slidable horizontally on a sleeve and used to raise and lower the stacked trays.
U.S. Pat. Nos. 3,601,282 to Vogel and 3,701,440 to Windstrup disclose mechanisms for denesting rimmed cartons or plates using spaced apart rods or blades which move reciprocally back and forth in parallel horizontal planes to alternately support and sequentially separate the lowermost carton or plate from the vertical stack. In the case of the Vogel '282 patent, the lowermost set of blades may also pivot to exert a prying force on the top of the rim of the lowermost plate.
While the denesting and dispensing mechanisms discussed above have a certain measure of utility in their particular applications, they have proven unsuitable for denesting deep plastic containers such as pails, particularly those fabricated from pliant plastics such as polyethylene, and those having a generally squared horizontal cross section opposed to a more circular horizontal cross section.
These types of pails become very difficult to denest due to the vacuum created between the pails if they are pressed together under weight, or when cooling after the manufacturing process. In these situations, it is not possible to generate a sufficiently strong and reliable vacuum in a gripping mechanism to grip and separate the pails without the vacuum releasing. The worm-type separators can simply strip or peel sections of the rim from the pail rather than separating the pails themselves, and are not as useful or practical when combined with a moving pail separating and conveying mechanism.